JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.8.23/jquery-ui.min.js"></script>
<div id="dialog">
   <label>Sample Date</label>
   <input id="cal"/>
</div>
<div id="results">

</div>

JavaScript

alert($.contains($('#dialog')[0], null))